_Hyla elaeochroa_ dispersed along Caribbean lowland routes. This species not only occurs in the wet forests of the Golfo Dulce region but also in Guanacaste. It is possible that _elaeochroa_ entered Guanacaste and moved to the Golfo Dulce region when the intervening area was less xeric than now (Duellman, 1966b). _Hyla elaeochroa_ extended its range to eastern Nicaragua, but even though northeastern Nicaragua has over 2,000 mm. of precipitation annually (Vivo Escoto, 1964), this species has not spread into Honduras and Guatemala. _Hyla boulengeri_ is widespread in Amazonian and northern South America, whereas _foliamorta_ occurs only in eastern Panamá and in north-central Colombia. The ancestral _boulengeri-foliamorta_ stock probably invaded Central America in the late Pliocene and dispersed through humid forested environments to Nicaragua. Apparently a peripheral population established itself in the dry Pacific lowlands of Panamá. This population differentiated from _boulengeri_ of the humid Caribbean lowlands and evolved into _foliamorta_, which subsequently expanded its range into Colombia. LITERATURE CITED BLAIR, W. F. 1960. Mating call as evidence of relations in the _Hyla eximia_ group. Southwestern Nat., 5(3):129-135. November 1. BOULENGER, G. A. 1882. Catalogue of the Batrachia Salientia s. Ecaudata, 2nd. ed., pp. 1-503, pls. 1-30. February. BROCCHI, P. 1881-1883. Etude des batraciens de l'Amerique Centrale. Mission Scientifique au Mexique et dans l'Amerique Centrale, Liv. 1, pp. 1-122, pls. 1-21. COCHRAN, D. M. 1955. Frogs of southeastern Brazil. Bull. U.S. Natl. Mus., 206:1-423. COPE, E. D. 1865. Third contribution to the Herpetology of Tropical America. Proc. Acad. Nat. Sci. Philadelphia, 17:195. 1876. On the batrachia and reptilia of Costa Rica. Jour. Acad. Nat. Sci. Philadelphia, new series, 8:93-154, pls. 23-28. 1887. Thirteenth contribution to the Herpetology of Tropical America. Proc. Amer. Philos. Society, 23:273. April. DAUDIN, F. M. 1802. Histoire naturelle des rainettes, des grenouilles et des crapauds. Paris, pp. 1-71, pls. 1-33. 1803. Histoire naturelle générale et particulière des reptiles. Paris, 8:1-439. DUELLMAN, W. E. 1956. The frogs of the hylid Genus _Phrynohyas Fitzinger_, 1843. Misc. Publ. Mus. Zool., Univ. Mich., 96:1-47, pls. 1-6. February 21. 1958. A monographic study of the colubrid snakes Genus _Leptodeira_. Bull. Amer. Mus. Nat. Hist., 114:1-152, pls. 1-31. February 24. 1960. A distributional study of the amphibians of the Isthmus of Tehuantepec, México. Univ. Kansas Publ., Mus. Nat. Hist, 13:19-72, pls. 1-8. August 16. 1963. Amphibians and reptiles of the rainforests of southern El Petén, Guatemala. Univ. Kansas Publ., Mus. Nat. Hist., 15:205-249, pls. 7-10. October 4. 1965. A biogeographic account of the herpetofauna of Michoacán, México. Univ. Kansas Publ., Mus. Nat. Hist., 15:627-709, pls. 29-36. December 30.